Solar power statistics
(TOA); the bottom image shows the annual insolation reaching the Earth's surface after passing through the atmosphere. Note that the two images use the same color scale.}} Solar (SI) is the per unit area (watt per square metre, W/m2), received from the in the form of as reported in the range of the measuring instrument. Solar irradiance is often over a given time period in order to report the emitted into the surrounding environment ( per square metre, J/m2), during that time period. This integrated solar irradiance is called solar irradiation, solar exposure, solar insolation, or insolation. Irradiance may be measured in or at the after absorption and . Irradiance in space is a of distance from the Sun, the , and cross-cycle changes. Irradiance on the Earth's surface additionally depends on the tilt of the measuring surface, the height of the sun above the horizon, and atmospheric conditions. Solar irradiance affects and animal behavior. The study and measurement of solar irradiance have several important applications, including the prediction of energy generation from s, the heating and cooling loads of buildings, and in climate modeling and weather forecasting. Measurement of solar irradiance There are several measured types of solar irradiance. * Total Solar Irradiance (TSI) is a measure of the over all wavelengths per unit area incident on the Earth's . It is measured to the incoming sunlight. The is a conventional measure of mean TSI at a distance of one (AU). * (DNI), or beam radiation, is measured at the surface of the Earth at a given location with a surface element perpendicular to the Sun. It excludes diffuse solar radiation (radiation that is scattered or reflected by atmospheric components). Direct irradiance is equal to the extraterrestrial irradiance above the atmosphere minus the atmospheric losses due to and . Losses depend on time of day (length of light's path through the atmosphere depending on the ), , content and other . The irradiance above the atmosphere also varies with time of year (because the distance to the sun varies), although this effect is generally less significant compared to the effect of losses on DNI. * Diffuse Horizontal Irradiance (DHI), or Diffuse Sky Radiation is the radiation at the Earth's surface from light scattered by the atmosphere. It is measured on a horizontal surface with radiation coming from all points in the sky excluding circumsolar radiation (radiation coming from the sun disk). There would be almost no DHI in the absence of atmosphere. * Global Horizontal Irradiance (GHI) is the total irradiance from the sun on a horizontal surface on Earth. It is the sum of direct irradiance (after accounting for the solar of the sun z'') and diffuse horizontal irradiance: \text{GHI} = \text{DHI} + \text{DNI} \times \cos (z) Solar power '''Solar power' is the from into , either directly using (PV), indirectly using , or a combination. Concentrated solar power systems use es or and to focus a large area of sunlight into a small beam. Photovoltaic cells convert light into an using the . Photovoltaics were initially solely used as a source of for small and medium-sized applications, from the powered by a single solar cell to remote homes powered by an rooftop PV system. Commercial concentrated solar power plants were first developed in the 1980s. The 392 MW installation is the largest concentrating solar power plant in the world, located in the of . As the cost of solar electricity has fallen, the number of grid-connected has and utility-scale s with hundreds of megawatts are being built. Solar PV is rapidly becoming an inexpensive, low-carbon technology to harness from the Sun. The current largest photovoltaic power station in the world is the 850 MW Solar Park, in , . The projected in 2014 that under its "high renewables" scenario, by 2050, solar photovoltaics and concentrated solar power would contribute about 16 and 11 percent, respectively, of the , and solar would be the world's largest source of electricity. Most solar installations would be in and . In 2017, solar power provided 1.7% of total worldwide electricity production, growing at 35% per annum. As of 2018, the unsubsidised for utility scale solar power is around $43/MWh. Photovoltaics }} A , or photovoltaic cell (PV), is a device that converts light into electric current using the . The first solar cell was constructed by in the 1880s. The German industrialist was among those who recognized the importance of this discovery. In 1931, the German engineer Bruno Lange developed a photo cell using in place of , although the prototype cells converted less than 1% of incident light into electricity. Following the work of in the 1940s, researchers Gerald Pearson, and Daryl Chapin created the solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%. The array of a , or PV system, produces direct current (DC) power which fluctuates with the sunlight's intensity. For practical use this usually requires conversion to certain desired voltages or alternating current (AC), through the use of . Multiple solar cells are connected inside modules. Modules are wired together to form arrays, then tied to an inverter, which produces power at the desired voltage, and for AC, the desired frequency/phase. Many residential PV systems are connected to the grid wherever available, especially in developed countries with large markets. In these , use of energy storage is optional. In certain applications such as satellites, lighthouses, or in developing countries, batteries or additional power generators are often added as back-ups. Such s permit operations at night and at other times of limited sunlight. Economics Cost – the PV learning curve |caption2=Solar PV – for Europe until 2020 (in euro-cts. per ) |caption3=Economic photovoltaic capacity vs installation cost in the United States with and without the federal (ITC) }} The typical cost factors for solar power include the costs of the modules, the frame to hold them, wiring, inverters, labour cost, any land that might be required, the grid connection, maintenance and the solar insolation that location will receive. Adjusting for inflation, it cost $96 per watt for a solar module in the mid-1970s. Process improvements and a very large boost in production have brought that figure down to 68 cents per watt in February 2016, according to data from Bloomberg New Energy Finance. California signed a wholesale purchase agreement in 2016 that secured solar power for 3.7 cents per kilowatt-hour. And in sunny large-scale solar generated electricity sold in 2016 for just 2.99 cents per kilowatt-hour – "competitive with any form of fossil-based electricity — and cheaper than most." Photovoltaic systems use no fuel, and modules typically last 25 to 40 years. Thus, capital costs make up most of the cost of solar power. Operations and maintenance costs for new utility-scale solar plants in the US are estimated to be 9 percent of the cost of photovoltaic electricity, and 17 percent of the cost of solar thermal electricity. Governments have created various financial incentives to encourage the use of solar power, such as programs. Also, s impose a government mandate that utilities generate or acquire a certain percentage of renewable power regardless of increased energy procurement costs. In most states, RPS goals can be achieved by any combination of solar, wind, biomass, , ocean, geothermal, , hydroelectric, hydrogen, or fuel cell technologies. Levelized cost of electricity The PV industry has adopted (LCOE) as the unit of cost. The electrical energy generated is sold in units of s (kWh). As a rule of thumb, and depending on the local , 1 watt-peak of installed solar PV capacity generates about 1 to 2 kWh of electricity per year. This corresponds to a of around 10–20%. The product of the local cost of electricity and the insolation determines the break even point for solar power. The International Conference on Solar Photovoltaic Investments, organized by , has estimated that PV systems will pay back their investors in 8 to 12 years. As a result, since 2006 it has been economical for investors to install photovoltaics for free in return for a long term . Fifty percent of commercial systems in the United States were installed in this manner in 2007 and over 90% by 2009. has said that, as of 2012, unsubsidised solar power is already competitive with fossil fuels in India, Hawaii, Italy and Spain. He said "We are at a tipping point. No longer are renewable power sources like solar and wind a luxury of the rich. They are now starting to compete in the real world without subsidies". "Solar power will be able to compete without subsidies against conventional power sources in half the world by 2015". Current installation prices In its 2014 edition of the Technology Roadmap: Solar Photovoltaic Energy report, the International Energy Agency (IEA) published prices for residential, commercial and utility-scale s for eight major markets as of 2013 (see table below). However, DOE's has reported much lower U.S. installation prices. In 2014, prices continued to decline. The SunShot Initiative modeled U.S. system prices to be in the range of $1.80 to $3.29 per watt. Other sources identify similar price ranges of $1.70 to $3.50 for the different market segments in the U.S., and in the highly penetrated German market, prices for residential and small commercial rooftop systems of up to 100 kW declined to $1.36 per watt (€1.24/W) by the end of 2014. In 2015, Deutsche Bank estimated costs for small residential rooftop systems in the U.S. around $2.90 per watt. Costs for utility-scale systems in China and India were estimated as low as $1.00 per watt. Grid parity Grid parity, the point at which the cost of photovoltaic electricity is equal to or cheaper than the price of , is more easily achieved in areas with abundant sun and high costs for electricity such as in and . In 2008, the levelized cost of electricity for solar PV was $0.25/kWh or less in most of the countries. By late 2011, the fully loaded cost was predicted to fall below $0.15/kWh for most of the and to reach $0.10/kWh in sunnier regions. These cost levels are driving three emerging trends: vertical integration of the supply chain, origination of s (PPAs) by solar power companies, and unexpected risk for traditional power generation companies, s and s. Grid parity was first reached in in 2013, and other islands that otherwise use ( ) to produce electricity, and most of the US is expected to reach grid parity by 2015. In 2007, 's Chief Engineer predicted grid parity without subsidies in sunny parts of the United States by around 2015; other companies predicted an earlier date: the cost of solar power will be below grid parity for more than half of residential customers and 10% of commercial customers in the , as long as grid electricity prices do not decrease through 2010. Productivity by location The productivity of solar power in a region depends on , which varies through the day and is influenced by and . The locations with highest annual solar irradiance lie in the arid tropics and subtropics. Deserts lying in low latitudes usually have few clouds, and can receive sunshine for more than ten hours a day. These hot deserts form the Global Sun Belt circling the world. This belt consists of extensive swathes of land in , , , , and , as well as the much smaller deserts of and . Africa's eastern , also known as the , has been observed to be the sunniest place on Earth according to NASA. Different measurements of (direct normal irradiance, global horizontal irradiance) are mapped below : File:SolarGIS-Solar-map-North-America-en.png|North America File:SolarGIS-Solar-map-Latin-America-en.png|South America File:SolarGIS-Solar-map-Europe-en.png|Europe File:SolarGIS-Solar-map-Africa-and-Middle-East-en.png|Africa and Middle East File:SolarGIS-Solar-map-South-And-South-East-Asia-en.png|South and South-East Asia File:SolarGIS-Solar-map-Australia-en.png|Australia File:SolarGIS-Solar-map-World-map-en.png|World Self consumption In cases of self consumption of the solar energy, the payback time is calculated based on how much electricity is not purchased from the grid. For example, in Germany, with electricity prices of 0.25 €/kWh and of 900 kWh/kW, one kWp will save €225 per year, and with an installation cost of 1700 €/KWp the system cost will be returned in less than seven years. However, in many cases, the patterns of generation and consumption do not coincide, and some or all of the energy is fed back into the grid. The electricity is sold, and at other times when energy is taken from the grid, electricity is bought. The relative costs and prices obtained affect the economics. In many markets, the price paid for sold PV electricity is significantly lower than the price of bought electricity, which incentivizes self consumption. Moreover, separate self consumption incentives have been used in e.g. Germany and Italy. Grid interaction regulation has also included limitations of grid feed-in in some regions in Germany with high amounts of installed PV capacity. By increasing self consumption, the grid feed-in can be limited without curtailment, which wastes electricity. A good match between generation and consumption is key for high self consumption, and should be considered when deciding where to install solar power and how to dimension the installation. The match can be improved with batteries or controllable electricity consumption. However, batteries are expensive and profitability may require provision of other services from them besides self consumption increase. s with electric heating with heat pumps or resistance heaters can provide low-cost storage for self consumption of solar power. Shiftable loads, such as dishwashers, tumble dryers and washing machines, can provide controllable consumption with only a limited effect on the users, but their effect on self consumption of solar power may be limited. Economics There have been major changes in the underlying costs, industry structure and market prices of solar photovoltaics technology, over the years, and gaining a coherent picture of the shifts occurring across the industry value chain globally is a challenge. This is due to: "the rapidity of cost and price changes, the complexity of the PV supply chain, which involves a large number of manufacturing processes, the balance of system (BOS) and installation costs associated with complete PV systems, the choice of different distribution channels, and differences between regional markets within which PV is being deployed". Further complexities result from the many different policy support initiatives that have been put in place to facilitate photovoltaics commercialisation in various countries. The PV industry has seen dramatic drops in module prices since 2008. In late 2011, factory-gate prices for crystalline-silicon photovoltaic modules dropped below the $1.00/W mark. The $1.00/W installed cost, is often regarded in the PV industry as marking the achievement of for PV. Technological advancements, manufacturing process improvements, and industry re-structuring, mean that further price reductions are likely in coming years. As of 2017 power-purchase agreement prices for solar farms below $0.05/kWh are common in the United States and the lowest bids in several international countries were about $0.03/kWh. , such as s, have often been offered to electricity consumers to install and operate solar-electric generating systems. Government has sometimes also offered incentives in order to encourage the PV industry to achieve the needed to compete where the cost of PV-generated electricity is above the cost from the existing grid. Such policies are implemented to promote national or territorial , job creation and reduction of which cause climate change. Due to economies of scale solar panels get less costly as people use and buy more—as manufacturers increase production to meet demand, the cost and price is expected to drop in the years to come. Solar cell efficiencies vary from 6% for amorphous silicon-based solar cells to 44.0% with multiple-junction . Solar cell energy conversion efficiencies for commercially available photovoltaics are around 14–22%. Concentrated photovoltaics (CPV) may reduce cost by concentrating up to 1,000 suns (through magnifying lens) onto a smaller sized photovoltaic cell. However, such concentrated solar power requires sophisticated heat sink designs, otherwise the photovoltaic cell overheats, which reduces its efficiency and life. To further exacerbate the concentrated cooling design, the heat sink must be passive, otherwise the power required for active cooling would reduce the overall efficiency and economy. Crystalline silicon solar cell prices have fallen from $76.67/Watt in 1977 to an estimated $0.74/Watt in 2013. This is seen as evidence supporting , an observation similar to the famous that states that solar cell prices fall 20% for every doubling of industry capacity. As of 2011, the price of PV modules has fallen by 60% since the summer of 2008, according to Bloomberg New Energy Finance estimates, putting solar power for the first time on a competitive footing with the retail price of electricity in a number of sunny countries; an alternative and consistent price decline figure of 75% from 2007 to 2012 has also been published, though it is unclear whether these figures are specific to the United States or generally global. The levelised cost of electricity ( ) from PV is competitive with conventional electricity sources in an expanding list of geographic regions, particularly when the time of generation is included, as electricity is worth more during the day than at night. There has been fierce competition in the supply chain, and further improvements in the levelised cost of energy for solar lie ahead, posing a growing threat to the dominance of fossil fuel generation sources in the next few years. As time progresses, renewable energy technologies generally get cheaper, while fossil fuels generally get more expensive: history for conventional ( ) solar cells since 1977.}} As of 2011, the cost of PV has fallen well below that of nuclear power and is set to fall further. The average retail price of solar cells as monitored by the Solarbuzz group fell from $3.50/watt to $2.43/watt over the course of 2011. For large-scale installations, prices below $1.00/watt were achieved. A module price of 0.60 Euro/watt ($0.78/watt) was published for a large scale 5-year deal in April 2012. By the end of 2012, the "best in class" module price had dropped to $0.50/watt, and was expected to drop to $0.36/watt by 2017. In many locations, PV has reached grid parity, which is usually defined as PV production costs at or below retail electricity prices (though often still above the power station prices for coal or gas-fired generation without their distribution and other costs). However, in many countries there is still a need for more access to capital to develop PV projects. To solve this problem has been proposed and used to accelerate development of solar photovoltaic projects. For example, offered, the first U.S. in the solar industry in 2013. Photovoltaic power is also generated during a time of day that is close to peak demand (precedes it) in electricity systems with high use of air conditioning. Since large-scale PV operation requires back-up in the form of spinning reserves, its marginal cost of generation in the middle of the day is typically lowest, but not zero, when PV is generating electricity. This can be seen in Figure 1 of this paper:. More generally, it is now evident that, given a carbon price of $50/ton, which would raise the price of coal-fired power by 5c/kWh, solar PV will be cost-competitive in most locations. The declining price of PV has been reflected in rapidly growing installations, totaling about 23 GW in 2011. Although some consolidation is likely in 2012, due to support cuts in the large markets of Germany and Italy, strong growth seems likely to continue for the rest of the decade. Already, by one estimate, total investment in renewables for 2011 exceeded investment in carbon-based electricity generation. In the case of self consumption payback time is calculated based on how much electricity is not brought from the grid. Additionally, using PV solar power to charge DC batteries, as used in Plug-in Hybrid Electric Vehicles and Electric Vehicles, leads to greater efficiencies. Traditionally, DC generated electricity from solar PV must be converted to AC for buildings, at an average 10% loss during the conversion. An additional efficiency loss occurs in the transition back to DC for battery driven devices and vehicles, and using various interest rates and energy price changes were calculated to find present values that range from $2,057 to $8,213 (analysis from 2009). For example, in Germany with electricity prices of 0.25 euro/kWh and of 900 kWh/kW one kWp will save 225 euro per year and with installation cost of 1700 euro/kWp means that the system will pay back in less than 7 years. References Category:Monetary system